Brake



T. P. CHASE 2,146;10

Feb. 7, 193.9.

BRAKE 2 Sheets-Sheet 1 Filed Feb. l, 1937 T. P. CHASE Feb. 7, 1939.

BRAKE 2 Sheets-Sheet 2 Filed Feb. l, 1937 Patented Feb. 7, 1939 v UNITED STATES BRAKE 'rama r. chase, nana, meh.,

General Motors Corporation, Detroit, Mich., a corporation of Delaware Application February l, 1937, Serial No. 123,391 Claim (CL 18S-152) This invention relates to brakes and has been designed more particularly for vuse on vehicles. The novel brake combines a hydraulic brake applying mechanism and an independent but as- 5 sociated emergency mechanical applying means, both .the mechanical and the hydraulic means operating upon a single pair oi.' shoes. The arrangement is such that equal pressures may be applied uponv the two shoes resulting in a balanced reaction between the shoes anddrum. It is also arranged such that the torque transmitted by the two anchor pins is equally divided, thereby minimizing drum distortion and avoiding displacement of the drum with reference to the brake assembly. The design also utilizes stronger springs at the anchored end of .the shoes than at the toe end to insure the holding of the trailing end of the shoes ilrmly against their anchorage. The invention, insofar as it relates to the applying means, involves mechanism whereby, when the shoes are applied by the hydraulic mechanism,` the applied forces are supplemented by self-actuating forces 'upon both shoes in the case of forward vehicle travel. `In the case o1 rearward travel the hydraulic-applying mechanism is supplemented by the self-actuating force of drum rotation kin the case of one shoe'only. When the shoes are applied by the mechanical spreading means, one shoe only is subject to the combined forces, the particular one being dependent upon the direction of drum rotation and vehicle travel.

An important feature of the invention is the simple mechanism by which the structure for the emergency mechanical operation is associated with and operates through parts of the hydraulic applying means.

Other objects and advantages will be understood from the followingV description.

In the drawings,

Fig. 1 is a vertical section through a brake drum showing the shoes and operating mechanism for the most part in elevation.

Fig. 2 is a section online 2-2 of Fig. 1.

Fig. 3 is a section on line 3-3 of Fig. l.

Fig. 4 is a section on line 4-4 of Fig. 1.

Fig. 5 is a view similar to Fig. 1 but showing a modiiied form.

50 Referring by reference characters to the drawings. numeral II is used to designate a conventional brake drumi This may be considered to be the drum used the ,reason that it is more commonly the rear v gliieels which have drums, the iioe withinwhih with a rear wheel o'i a vehicle iorv PATENT OFFICE assignor to are applied in service by hydraulic means and which are also adapted to be applied by a mechanical hook-up associated with an emergency lever.

Numeral I3 is used to designate the conven- 5 tional cover plate or backing plate. This plate is as usual secured to an axle housing flange as at I5. Within the brake drum are shoes I1 and I9. Secured to the cover plate are anchor pins 2I and 23 located diametrically opposite each other. 10 Shoe I1 is mounted to anchor on pin 2I through the instrumentality of articulating links 21 and 21a. These links are pivoted to the shoe I1 on opposite sides of its web by a pin 25. Limited movement of the links about the pin is provided by mechanism marked 29 more fully described below. The ends of the links are recessed to engage the pin 2| as clearly illustrated by Fig- 1.

In a similar way links 33 and 33a. are pivoted to shoe I9 on pin 35 -andrthese links anchor on 20 pin 23. Limited movement is provided at .31. Fig. 4 shows in detail the relation of shoe I9, links 33, 33a and anchor pin 23. It will be seen that surrounding the 'pin 35 and between the web oi' shoe I9 and theends of the links' 33, 25 33a are spacing sleeves 39. The construction marked 31 on Fig. 1 and illustrated more speciiically in Fig. 4 comprises a pin 4I carried by the shoe web and extending through enlargedopenings I3 in the links 33 and 33a, the openings 30 being dimensioned to aii'ord the limited swinging of the links about the pivot pin 35. Springs 45 surround the pin 4I and by their pressure on the links resist the rotation of the links. Substantially the same construction is employed in the 35 case of shoe I1 and its links 21, 21a.

Between one pair of adjacent ends of shoes I1 and I9 (the ends identiiied by anchor pin 23) is a hydraulic cylinder 41 within which reciprocates a piston I9 having a sealing cup 5I. A cap 40 53 surrounds the open end oi the cylinder and may engage the wall of said open end. This cap is also engaged by the end wall of the piston as is shown in Fig. 1. A screw 55 terminates in an eye 51 pivoted to shoe I1 by pin 59. The screw a freely 'enters the hollow piston but is threaded to the nut 8l. The nut 6I carries a peripherally notched part whereby it may be rotated and the screw reclprocated to adjust the clearance between the shoe and the drum. The cylinder 41 50 has at its closed end a projection 63 which is pivoted on the anchor pin 23 between the links 33 and 33a as shown by Fig. 4. Hydraulic medium from a suitable master cylinder, not illustrated, is transmitted by means o! a pipe 35 to cylinder 41 between its closed end and the piston. From cylinder 41a pipe 61 carries the uid to a second cylinder 69 located between the other pair of adjacent ends' of the shoes. Any convenient air bleed may be provided in boss 1I in the cylinder 69 at the uppermost part of the cylinder.

Cylinder 69 is provided with a piston 49 like that of cylinder 41 and the connections of'this piston with the adjacent end of shoe I9 are the same as vthe connections between the shoe I1 and the piston 49 of cylinder 41. The projection 13 of cylinder 69 is longer than its counterpart 63 of cylinder 41 and this projection I3 is not anchored on anchor pin 2| as was the case of the projection 63. Instead of being so/ anchored, it is pivoted to and betweenspaced arms 15 and 11 by a pin 19, the arms extending between the links 21 and 21a. 'Ihe arms 15 and 11 lie on opposite sides of the web of the shoe and are pivoted thereto by a pin 8|. In Fig. 1 link 21 is broken away to show a roller 83 carried on a pin 85 lwhich is supported by arms 15 and 11. This roller is adapted to engage. the edge of the web of the shoe I1. One of the arms is extended to form a lever 11a. The' end of the lever is connected by a cable 81 passing through an opening 89 in the cover I3 and this cable is adapted t0 be attached to an emergency lever hook-up of any preferred kind.

Numeral 9| `is used to designate any convenient form of shoe holding device to retain the shoe axially toward or against the cover plate. At 93 and 95 are springs flxedly anchored as at 94 at their adjacent ends and connected to the shoes at their outer ends. It will be noted that springs 93 pull upon the shoes at their ends adjacent the anchor pins. Because of the location of the points of attachment, these springs 93 pull uponv the shoes adjacent their pivoted ends more forcibly than thesprings 95 pull upon the other ends. By this arrangement the engagement of the shoes with their anchor pins is insured. It will be noted that In the region adjacent anchor 2|,`

spring 93 pulls shoe I'I so that it anchors on anchor l2|, and that spring 95 pulls shoe I9 so that projection 13 of cylinder 69 moves and causes roller 83 to contact the edge of shoe I1.

The operation is as follows: vWhen fluid is forced into cylinder 41, since the cylinder is anchored on pin 23, the movement is confined to the piston which pushes the shoe I1 against the drum, the shoe anchoring by means of its links 21, 21a, upon the pin 2| when the drum is turn- -ing clockwise, the direction intended to correspond with forward vehicle travel. 'I'he uild pressure transmitted by pipe 61 to cylinder 69 cannot move this cylinder 69 to any appreciable extent because its position is xed, owing to the contact of the roller 83 with the web of the shoe I1, that shoe being now held to its anchorage as explained above. The whole movement, therefore, is confined to the piston, which movement applies shoe I9. Owing to the direction of drum rotation, this shoe is also self-actuating. It will therefore be seen that for forward vehicle travel the hydraulic forces in the case of each shoe supplement the force of self-actuation and the brake action is highly effective in resisting drum roe, tation. In checking reverse rotation, the self-- actuating force in the case of shoe I9, is opposed by the hydraulic force applied by cylinder 69.

Shoe I1, actuated both by self-actuatingforce and by hydraulic means, (cylinder 69) anchors on pin 23 through the engagement of the cap 53 with the end of cylinder 41. In this case, therefore, shoe .I1 is more effective than shoe I9 since both hydraulic and self-actuating v' forces are effective on shoe I1 to rotate it against the drum. For emergency operation the lever 11a is rocked in a counter-clockwise direction (see Fig. l). Roller 83 ceases to contact shoe I1 and a conventional two-shoe operation is effected by means of a pivoted connection at 8| with shoe I1 and a link connection draulic cylinder 69 with shoe I9, the pin 2| being the anchorage pin in this case-for both shoes.

It will be seen that by these simple arrangements the several advantages of effective brake operation with balanced pressures as set forth 15 ment of shoes and applying means, the difference 20 being that the articulated linkage between the shoes and their anchor pins are omitted. Shoe I1 directly engages its anchor 2| and shoe I9' directly engages its anchor pin 23. Similar reference characters are used to illustrate the corresponding parts. The operation is the same as before with the exception that the better conformity of the shoes to the drum aiforded by the articulating linkage is sacrificed.

I claim: v

1. In a brake, opposed shoes, an operating lever, pivot means between said lever and one end of a first shoe, said lever having contact means spaced from its shoe pivot and adapted to engage said first shoe, a reciprocating link connected to said lever and to said second shoe adjacent the end thereof, said link including as a part thereof fluid pressure means, an anchor pin for said .first shoe between the adjacent shoev ends, a second anchor pin between the opposite pairs of adjacent ends of said shoes, the second shoe adapted to engage said second anchor, and a second fluid pressure means secured to said second anchor and operable on the first shoe, said fluid pressure means and reciprocable linkv connection each having engaging parts whereby they act as rigid links.

2. In a brake drum, oppositely disposed first and second-shoes, anchor means between each pair of adjacent ends, the first shoe adapted to engage one anchor means and the second means adapted to. engage the second anchor means, hydraulic shoe applying means between each pair of adjacent ends and .comprising parts mounted for relative axial movement, one of said lastnamed parts being attached to each shoe at the end remote from the shoe anchorage, the other part of one of said hydraulic applying means attached to the adjacent-anchor means, means pivoted to the other part of the other hydraulic applying means and to the first shoe and having a member adapted to contact said first shoe.

3. 'I'he invention defined by claim 2, said last- ,named means including a rigid lever extension whereby when said means and extension is rocked about its pivotalconnection with the first shoe the shoes may be mechanically applied, the hydraulic applying means acting as thrust links.

4. In a brake, opposed shoes having a pair of vadjacent ends, an operating lever, pivot means shoes adlacentits said end, said link including f through the hylo eol relatively reciprocable parts, means to force fluid under pressure between said parts, an anchor adjacent said ends and 4adapted to be engaged by l the rst of said shoes and yielding means to move said rst shoe against its anchor and to move said second shoe and link so that said contact means contacts said rst shoe. 

